Traditional apparatus and methods for classifying materials include various types of fixed separation systems. Those systems are conventionally permanent installations and, typically the aggregates are transported to and from the permanent installations for purposes of classification. It will be appreciated that the handling of the aggregate materials, as well as their transportation to and from these permanent sites incurs substantial expenses in labor, vehicle operation, maintenance and travel time. As an example, the traditional method of sizing asphalt filler sands for highway projects uses conventional portable wash screens. Filler sand is washed by flooding the screen with water. The -200 mesh slurry is then pumped into settling ponds. The sand product has a moisture content which must then be dried prior to adding to the asphalt mixture. While this process has been found acceptable, its various disadvantages include the fuel expense of drying the wet material, the environmental impact of settling ponds. the requirement for trucking wash water to remote sites and generally the transportation of the aggregate to and from the sites. Even where dry particulate separation devices are employed at permanent sites, there is incurred the substantial additional cost in transportation, fuel and associated environmental problems.